How to read a function definition (prototype)

Each function in the manual is documented for quick reference. Knowing how
to read and understand the text will make learning PHP
much easier. Rather than relying on examples or cut/paste, everyone should
know how to read function definitions (prototypes). Let's begin:

Type of value this function returns, which is an
integer (i.e. the length of a string is measured in
numbers).

( string $string )

The first (and in this case the only) parameter/argument for this
function is named string, and it's a
string.

We could rewrite the above function definition in a generic way:

returned type function name ( parameter type parameter name )

Many functions take on multiple parameters, such as in_array().
Its prototype is as follows:

bool in_array ( mixed $needle, array $haystack [, bool $strict])

What does this mean? in_array() returns a
boolean value, TRUE on
success (if the needle was found in the
haystack) lub FALSE w przypadku niepowodzenia (if the
needle was not found in the
haystack). The first parameter is named
needle and it can be of many different
types, so we call it
"mixed". This mixed needle
(what we're looking for) can be either a scalar value (string, integer,
or float), or an
array.
haystack (the array we're searching in) is the
second parameter. The third optional parameter is
named strict. All optional parameters are seen
in [ brackets ]. The manual
states that the strict parameter defaults to
boolean FALSE. See the manual page on each function for details on
how they work.

There are also functions with more complex PHP version information. Take
html_entity_decode() as an example:

(PHP 4 >= 4.3.0, PHP 5)

This means that this function has only been
available in a released version since PHP 4.3.0.